Snap switch



y 1962 J. SCHMIDINGER 3,037,102

SNAP SWITCH Filed Feb. 6, 1961 l N V N TO R JfEPH mm/m n United States Patent 3,037,102 SNAP SWITCH Joseph Schmidinger, RD. 1, Assembly Point, Lake George, N.Y. Filed Feb. 6, 1961, Ser. No. 87,270 8 Claims. (Cl. 200-88) The present invention relates to expansible wire controlled snap switches, more particularly to the type wherein an expansible wire moves the free end of a snap member to different circuit controlling positions with a snap action, and comprises a novel switch of this type which is simple to construct, precise in operation, of long useful life and of a wide field of application. The new switch which may be operated as a flasher, a relay, a time switch, an overload protector or a voltage regulator depending upon the circuit connections, is an improvement over the wire controlled snap switch disclosed and claimed in Schmidinger Patent 2,761,931 dated September 4, 1956.

The switch of the present invention can be made insensitive to current and voltage fluctuations, will operate over a wide range of current values and develops posi tive and firm contact pressure with extremely low wattage consumption for its operation.

The new switch comprises a metal plate member of improved construction adapted to be mounted at one end and carrying one or more contacts at its free end, the plate being provided with two generally longitudinal slots which terminate short of the ends or" the plate and define a central strip. The central strip is biased at both ends and a pull wire, which is secured to the strongly biased section of the strip adjacent the fixed end of the plate extends substantially parallel to the plate. The bias of the two ends of the strip is such that the strip assumes a natural bow shape before the wire is tensioned. When the wire is tensioned, the strip assumes the form of a generally M-shaped curve with the initially unstressed intermediate portion of the strip forming the depression of the M. During operation of the switch, the radii of curvatures of the parts of the strip vary in magnitude but not in sign. One or more fixed contacts or stops are positioned adjacent the free end of the plate for engagement therewith, the free end snapping into and out of contact closing position with change in tension in the wire.

An important feature of the above briefly described switch is the combination of the biased strip with the tensioned wire exerting a generally longitudinal pull on the strongly biased part of the strip. This feature insures that all the motive power supplied by the expanding and contracting wire is transmitted to and utilized by the central portion of the strip for causing the free end of the plate to snap from one position to another and is one reason why it is possible to employ relatively short wires. This feature also aids to a considerable extent, the natural and unfailing transformation of the described single bow into the characteristic double bow or generally M shape of the strip. The generally longitudinal disposition of the pull wire is also advantageous from a constructural point of view as it allows extremely cornpact unit design.

The slots defining the central strip of the snap plate are preferably so shaped as to reduce the width of the central portion of the strip. The longitudinal side portions of the strip of the plate are crimped to increase the length of the central strip with relation to the overall length of the plate.

Change in tension of the pull wire for operation of the switch occurs as a result of passage of current therethrough as in conventional pull wire switches. The new ice switch may be designed for series or shunt operation as desired.

For a better understanding of the invention and of switches embodying the invention reference may be had to the accompanying drawing of which:

FIG. 1 is a plan view of the new snap plate for use in a snap switch embodying the invention;

Fig. 2 is a side view of an adjusted switch connected in a circuit and explanatory of the operation of the switch as a flasher;

FIG. 3 is a side view showing the preferred construction of the switch diagrammatically illustrated in FIG. 2; and

FIGS. 4 and 5 are respective views of the snap switch of FIG. 3 looking in the direction of the arrows 4 and 5.

The invention will be first described with reference to FIGS. 1 and 2. These figures are directed primarily to the snap plate of the switch but FIG. 2 includes, at least diagrammatically, sufiicient of the parts associated with the snap plate to make clear the construction, adjustment and operation of a switch incorporating the plate. The snap plate illustrated in FIGS. 1 and 2 comprises a rectangular plate 2 provided with two slots 4-4 which extend for the major length of the plate. The slots 4@ define a central strip 6 which varies in width from a minimum adjacent the central section to a maximum at the closed ends of the slots. Each side portion 8 of the plate is provided with a crimp 10 which shortens its length relative to that of the central strip 6. One end 12, which when the plate is mounted becomes the free end of the plate, is formed with a central raised section 14 which merges into the adjacent end of the central strip 6. This raised portion 14 provides the bias at the free end of the plate and insures against reversal of curvature of the central strip during operation of the device. The raised portion or bias 14, in conjunction with the crimps 10, causes the adjacent end of the central strip 6 to curve upwardly from the body of the plate as viewed in FIG. 2. The metal of the plate adjacent the other end of the central strip 6 is forced upwardly away from the plane of the plate as indicated at 16 to provide a bias at that end of the plate which likewise insures that the strip adjacent that end will bow outwardly from the plane of the plate as shown in FIG. 2. Preferably, as shown best in FIG. 1, the width of the central strip is slightly greater at the end adjacent the bia 16. This end of the plate is welded or otherwise secured to a frame element 18 of the switch and the other or free end of the plate carries a contact member 20. An L-shaped anchor member 22 of round stock has one leg welded to the concave side of the strip 6 adjacent the fixed end of the plate and its other leg curved into a loop which supports an insulating head 24. The frame 18, which is shown only diagrammatically in FIG. 2 and will be described in more detail in connection with FIGS. 3 through 5, has a finger 26 bent out therefrom. The free end of the finger is in general alignment with the bead 24. An expansible pull wire 28 is secured to the finger 26 and anchored in the bead 24. Beyond the head 24 the Wire 28 is formed into a ballast resistance 30 and is connected to a fixed contact 32 adapted to be engaged by the plate carried contact 20 in one position of the plate.

After mounting the snap plate on the frame element and attaching the pull wire to the anchoring finger 26 the switch is adjusted by bending or moving the finger to increase the tension in the pull wire. The introduction of tension into the pull wire provides a longitudinal pull on the central strip which causes the intermediate central section of the strip to go into concavity while the end sections of the central strip remain in convexity. In

this position pressure begins to build up between contacts 2t) and 32. When the tension is further increased by movement of the finger 26, sufficient force is provided to cause the central portion of the strip 6 to pass beyond the plane of the plate and assume the contour of a relatively flat M as shown in FIG. 2. At a given tension in the pull Wire the central part of the plate is forced through a position of unstable equilibrium at which instant some of the force accumulated in the strip by the longitudinal pull of the wire is released and operates to snap the free end of the plate with the contact away from contact 32. The switch is now in adjustment. A switch so adjusted may be connected in a circuit such as that shown diagrammatically in FIG. 2. As shown in that figure the frame 13 may be connected to a source of positive potential indicated by the plus sign. The fixed contact 32, which is insulated from the frame 18, may be connected through a relay winding 34 to a lamp 36 to be flashed. The armature 38 of the relay may be connected to the source of positive potential and a front contact associated with the armature may be connected through a pilot lamp 4%) to the negative terminal of the source, shown as ground. Thus, when the source of energy is connected to the frame 1% and the pull Wire 28 is cold, current will flow from the source to the frame, through the finger 26, pull wire 28, resistor 30, relay winding 34 and lamp 136 to the negative terminal of the source. This current, because of the inclusion of the ballast resistor 36, will be insuflicient to energize the relay or to light the lamp 36. The current, however, will heat the pull wire 28 and permit it to expand. Expansion of the pull wire releases the tension therein sufficiently to permit the plate 2 to snap into contact closing position. In this position the pull wire 28 and resistor 30 are shunted from the circuit of the relay 34 and lamp 36. Accordingly the lamp 36 lights and the relay winding 34 attracts its armature to close the circuit of the pilot lamp 40. The pull wire 28, being shunted, cools and contracts. When the tension in the pull wire returns to its initial value the plate snaps to contact open position and the lamps 36 and 40 are extinguished.

By constructing and assembling the device in the manner described above, it has been found that the central strip is always in complete functional control over extremely wide speed ranges and allows the splitting of the one and off periods in infinite degrees. The reason for this unusual control is that the biased sections of the strip always remain in convexity, while the central section always remains in concavity and therefore only the amplitudes of the respective curvatures are changed during the operation of the device. Since no reversal of any of the three curvatures occurs, the mere changing of amplitudes can be caused by very slight expansion of the pull wire which can therefore be very short per given power (wattage) used to expand it and relatively thin since it will never be subjected to the harsh shocks which are characteristic with reverse buckling members. These statements are supported by successful tests with pull wires of one inch in length and of .002 inch in diameter and also by tests with a flasher made in the manner described which flashed at 75 cycles per minute a 150 milliampere lamp connected in series with a pull wire only 1 long, the device operating at a terminal drop of only 0.1 volt.

It should be noted that the closely spaced parallel arrangement of the two longest parts, the pull wire 23 and the plate 2 not only allows extremely compact unit design, but contributes to a large degree to the functional efficiency of the device since the horizontal motion of the wire 28 is converted by the short anchor member 22 into perpendicular motion of the vital central section of the strip 6. Since the anchor member 22 is much shorter than the distance between the point of its attachment to the strip and the central concave section of the strip 6, motion amplifying leverage is effected so that the slight movement of the anchor member results in relatively large movement of the central section of the strip 6. The changing of the amplitudes of the three curvatures previously described is greatly smoothed by this system of conversion of horizontal into perpendicular motion and is one of the reasons why this device will function efiiciently with much lighter tensile loading of the pull wire than would be possible for example if the central strip were pulled or pushed perpendicularly relative to its plane.

In FIGS. 3 through 5 a compact rugged physical embodiment of the switch of the invention is shown. The switch is supported on a base 42 of insulating material, such as phenol. formaldehyde resin, in which are anchored three prong terminals 44, 46 and 43 by means of lugs or tongues which extend through the base 42. The frame 18 has an offset lower portion 50 which rests on the base 42 over the terminal 48 and is clamped to the base by lugs 5' 2 of that terminal. The frame is provided with a generally square opening 54 within which a support 56 for the fixed contact 32 is disposed. Support 56 includes a lower generally square plate element 56a which is clamped to the lower part of frame 18 by inturned flanges 53 of the frame, spacers of mica or the like on each side of the plate element electrically insulating the element from the frame. The contact 32 is welded to one face of the support 56 within the opening 54 of thefr-arne. A rearwardly extending tab 56!) on the support 56 provides means for adjusting the position of the fixed contact. One end of winding 34 is welded to the tab 56b and the other end of the winding is welded to a lug of terminal 46. For electrical connection of the contact 32 to the resistance coil 30, the plate element 56a is provided with an outwardly extending finger 560.

Also clamped between the flanges 58 and electrically insulated therefrom and from the plate element 56a by mica spacers, is a plate element 663a forming a lower extension of a support arm 60 for a stop 62. The stop 62 is aligned with contact 32 and has an outwardly extending tab 681) thereon for adjustment of the spacing of the stop from the snap plate 2.

Winding 34 has a U-shaped core 63 the lower leg of which is welded to a finger 64 extending outwardly and rearwardly, as viewed in FIG. 4, from the frame 18 and formed integral therewith. The lower end of the armature 33 is spring mounted on the lower end of the core 63. The upper end of the armature carries an electrical contact aligned with a fixed contact 66. Contact 66 is carried by an arm 68 insulatedly mounted on the upper end of the core 63. Also mounted on the upper end of the core 63 is an arm 7%) (shown best in FIG. 5) that has upper and lower spaced fingers, the former serving as a back stop for the armature and the latter serving as a stop for the upper end of a leaf spring 72. Spring 72, the lower end of which is secured to the lower end of the armature, biases the armature toward retracted position. Terminal 44 is connected by a wire 74 with an extension of arm 68. In order to protect pull wire 28 from heat radiated from resistance winding 39 during operation of the device, a mica shield 76 is positioned between the winding and the frame. The upper end of frame 13 is formed along its sides with portions 78 offset from the plane of the frame to provide spaced areas to which the snap plate 2 is welded. The lower end of the snap plate extends between the contact 32 and stop 62 with the plate carried contact 20 aligned with the contact 32. A suitable cover (not shown in the drawing) that is crimped to the periphery of the base 42 completes the assembly.

As the operation of the device of FIGS. 3, 4 and 5 has already been described with reference to the diagram of FIG. 2 no detailed discussion thereof is now necessary. In use, a source of energy is connected through a suitable switch to terminal 48, a lamp load to be flashed is connected to terminal 46 and a pilot lamp is connected to terminal 44. When the circuit to terminal 48 is closed, current flows through the frame, finger 26 thereof, pull wire 28, resistance coil 30, plate element 56a, support 56, tab 56b, winding 34 to terminal 46 and thence to the lamp load. This current is insufficient to light the load or to cause attraction of armature 38. The current is sufiicient to heat the pull wire 28 which thereupon releases the tension on the snap plate so that the plate snaps into position to close contacts 20 and 32. Closure of contacts 20 and 32 shunts the pull wire 28 and resistance 30 from the circuit, thereby increasing the current through the lamp load and through the Winding 34. The lamp load is then lighted and the circuit for the pilot lamp closed by engagement of the armature carried contact with contact 66. The circuit for the pilot lamp can be traced from terminal 48, frame 18, frame extension 64, core 63, armature 38, contact 66, wire conductor 74 to terminal 44 and pilot lamp.

The improved snap plate of the invention and of a specific flasher construction embodying the same has now been described. Obviously various features of the described flasher could be changed without departing from the spirit of the invention or the scope of the accompanying claims. For example, if pilot indication is not desired the parts of the flasher coupled to the pilot lamp circuit could be omitted or if an alternator rather than a flasher were desired the stop 62 could be replaced by a contact and circuit connections made thereto for completion of a circuit in the position of the snap plate corresponding to maximum tension in the pull means. Instead of a wire pull means, a metallic ribbon could be employed. Other variations within the spirit of the invention will be apparent to those skilled in the art.

The following is claimed:

1. In a snap switch, the combination comprising a resilient rectangular plate of electrically conducting material having two longitudinal closed ended slots therein defining a. central vane that is narrowest along its central section, the plate being deformed adjacent each end of the vane to bias the vane outwardly from the plane of the strips of the plate on the outer sides of the slots, each of said strips having a crimp therein which shortens the length thereof relative to the length of the vane, a frame of conducting material having means thereon for mounting one end of the plate, an electrical contact secured to the plate adjacent the other end thereof and on the side thereof toward which the ends of the vane are concave, an L- shaped anchor member having one leg secured to the vane on the convex side thereof adjacent the mounted end of the plate, a pull means insulatedly anchored in the other leg of said member, a bendable finger integral with said frame to which said pull means is secured under tension sufficient to how the central part of the vane oppositely to the biased ends thereof and a fixed contact insulated from the frame and positioned for engagement by said plate carried contact when the tension in said pull means reduces as a result of current therethrough.

2. The combination according to claim 1 wherein the said slots are straight sides along their outer edges and curved along their inner edges to define a vane that is widest at the mounted end of the plate.

3. The combination according to claim 2 wherein said frame is formed with spaced offset portions to which the strips of the plate are welded adjacent the wider end of the vane.

4. The combination according to claim 1, a relay including a winding, a core, and an armature spring mounted at one end on said core, means mounting said core on said frame, a ballast resistor connected between the end of said pull means insulatedly anchored in said L-shaped anchor member and said fixed contact, a first terminal electrically connected to said frame and adapted for connection of a source of electrical energy thereto, a second terminal insulated from said fname and adapted for connection to a lamp load to be flashed, said relay winding being connected between said fixed contact and said second terminal, a second fixed contact insulated from said frame and positioned for engagement by said relay armature when in attracted position and a third terminal insulated from said frame and connected to said second contact, said third terminal being adapted to be connected to a pilot signal.

5. The combination according to claim 4 including means connected to said first mentioned fixed contact for adjusting the position thereof, said means serving also for connection to one end of said relay winding.

6. The combination according to claim 1, means comprising a thin mica piate for shielding said pull means from heat radiated by said ballast resistor during operation of the switch.

7. The combination according to claim 1 including stop means mounted on said frame and positioned in alignment with said fixed contact for engagement with said plate when the pull means is not carrying current.

8. The combination according to claim 1 wherein the bias at the end of the vane adjacent the free end of the plate is provided by a raised generally planar portion of the end of the plate and the bias at the end of the vane adjacent the mounted end of the plate is a stronger bias and is provided by forming the metal of the vane end outwardly from the plane of the plate with a curvature concave toward the frame.

References Cited in the file of this patent UNITED STATES PATENTS 2,249,837 Lee July 22, 1941 2,639,345 Sitzer May 19, 1953 2,689,283 Pulvari Sept. 14, 1954- 2,761,931 Schmidinger Sept. 4, 1956 2,788,414 Cromwell et a1. Apr. 9, 1957 2,820,120 Flatt et al. Jan. 14, 1958 FOREIGN PATENTS 1,085,267 France July 21, 1954- 552,181 Italy Nov. 28, 1956 

